Buggy code:
public class CliClient { public enum Function { BYTES ( BytesType . instance ) , INTEGER ( IntegerType . instance ) , LONG ( LongType . instance ) , LEXICALUUID ( LexicalUUIDType . instance ) , TIMEUUID ( TimeUUIDType . instance ) , UTF8 ( UTF8Type . instance ) , ASCII ( AsciiType . instance ) , COUNTERCOLUMN ( CounterColumnType . instance ) ; private AbstractType validator ; Function ( AbstractType validator ) { } public AbstractType getValidator ( ) { } public static String getFunctionNames ( ) { } } private enum AddKeyspaceArgument { PLACEMENT_STRATEGY , STRATEGY_OPTIONS , DURABLE_WRITES ; } protected enum ColumnFamilyArgument { COLUMN_TYPE , COMPARATOR , SUBCOMPARATOR , COMMENT , ROWS_CACHED , ROW_CACHE_SAVE_PERIOD , KEYS_CACHED , KEY_CACHE_SAVE_PERIOD , READ_REPAIR_CHANCE , GC_GRACE , COLUMN_METADATA , MEMTABLE_OPERATIONS , MEMTABLE_THROUGHPUT , MEMTABLE_FLUSH_AFTER , DEFAULT_VALIDATION_CLASS , MIN_COMPACTION_THRESHOLD , MAX_COMPACTION_THRESHOLD , REPLICATE_ON_WRITE , ROW_CACHE_PROVIDER , KEY_VALIDATION_CLASS ; } private static final String DEFAULT_PLACEMENT_STRATEGY = "org.apache.cassandra.locator.NetworkTopologyStrategy" ; private final String NEWLINE = System . getProperty ( "line.separator" ) ; private final String TAB = "<seq2seq4repair_space>" ; private Client thriftClient = null ; private CliSessionState sessionState = null ; private String keySpace = null ; private String username = null ; private Map < String , KsDef > keyspacesMap = new HashMap < String , KsDef > ( ) ; private Map < String , AbstractType > cfKeysComparators ; private ConsistencyLevel consistencyLevel = ConsistencyLevel . ONE ; private CliUserHelp help ; public CliClient ( CliSessionState cliSessionState , Cassandra . Client thriftClient ) { } private CliUserHelp getHelp ( ) { } public void printBanner ( ) { } public void executeCLIStatement ( String statement ) { } private void cleanupAndExit ( ) { } public KsDef getKSMetaData ( String keyspace ) throws InvalidRequestException , NotFoundException , TException { } private void executeHelp ( Tree tree ) { } private void executeCount ( Tree statement ) throws InvalidRequestException , TimedOutException , UnavailableException , TException { } private void executeDelete ( Tree statement ) throws InvalidRequestException , TimedOutException , UnavailableException , TException { } private void doSlice ( String keyspace , ByteBuffer key , String columnFamily , byte [ ] superColumnName , int limit ) throws IllegalAccessException , InstantiationException , NoSuchFieldException , InvalidRequestException , NotFoundException , TimedOutException , UnavailableException , TException { } private AbstractType getFormatType ( String compareWith ) { } private void executeGet ( Tree statement ) throws ClassNotFoundException , IllegalAccessException , InstantiationException , NoSuchFieldException , InvalidRequestException , NotFoundException , TimedOutException , UnavailableException , TException { } private void doGetCounter ( ByteBuffer key , ColumnPath path ) throws ClassNotFoundException , IllegalAccessException , InstantiationException , NoSuchFieldException , InvalidRequestException , NotFoundException , TimedOutException , UnavailableException , TException { } private void executeGetWithConditions ( Tree statement ) { } private void executeSet ( Tree statement ) throws IllegalAccessException , InstantiationException , NoSuchFieldException , InvalidRequestException , TimedOutException , UnavailableException , TException { } private void executeIncr ( Tree statement , long multiplier ) throws ClassNotFoundException , IllegalAccessException , InstantiationException , NoSuchFieldException , InvalidRequestException , NotFoundException , TimedOutException , UnavailableException , TException { } private void executeShowClusterName ( ) throws TException { } private void executeAddKeySpace ( Tree statement ) { } private void executeAddColumnFamily ( Tree statement ) { } private void executeUpdateKeySpace ( Tree statement ) { } private void executeUpdateColumnFamily ( Tree statement ) { } private KsDef updateKsDefAttributes ( Tree statement , KsDef ksDefToUpdate ) { } private CfDef updateCfDefAttributes ( Tree statement , CfDef cfDefToUpdate ) { } private void executeDelKeySpace ( Tree statement ) throws InvalidRequestException , NotFoundException , SchemaDisagreementException , TException { } private void executeDelColumnFamily ( Tree statement ) throws InvalidRequestException , NotFoundException , SchemaDisagreementException , TException { } private void executeList ( Tree statement ) throws IllegalAccessException , InstantiationException , NoSuchFieldException , CharacterCodingException , InvalidRequestException , NotFoundException , TimedOutException , UnavailableException , TException { } private void executeDropIndex ( Tree statement ) { if ( ( ! ( CliMain . isConnected ( ) ) ) || ( ! ( hasKeySpace ( ) ) ) ) return ; String columnFamily = CliCompiler . getColumnFamily ( statement , keyspacesMap . get ( keySpace ) . cf_defs ) ; <START_BUG> String rawColumName = statement . getChild ( 1 ) . getText ( ) ; <END_BUG> CfDef cfDef = getCfDef ( columnFamily ) ; ByteBuffer columnName = columnNameAsBytes ( rawColumName , cfDef ) ; boolean foundColumn = false ; for ( ColumnDef column : cfDef . getColumn_metadata ( ) ) { if ( column . name . equals ( columnName ) ) { foundColumn = true ; if ( ( column . getIndex_type ( ) ) == null ) throw new RuntimeException ( String . format ( "Column<seq2seq4repair_space>'%s'<seq2seq4repair_space>does<seq2seq4repair_space>not<seq2seq4repair_space>have<seq2seq4repair_space>an<seq2seq4repair_space>index." , rawColumName ) ) ; column . setIndex_name ( null ) ; column . setIndex_type ( null ) ; } } if ( ! foundColumn ) throw new RuntimeException ( String . format ( "Column<seq2seq4repair_space>'%s'<seq2seq4repair_space>definition<seq2seq4repair_space>was<seq2seq4repair_space>not<seq2seq4repair_space>found<seq2seq4repair_space>in<seq2seq4repair_space>ColumnFamily<seq2seq4repair_space>'%s'." , rawColumName , columnFamily ) ) ; try { String mySchemaVersion = thriftClient . system_update_column_family ( cfDef ) ; sessionState . out . println ( mySchemaVersion ) ; validateSchemaIsSettled ( mySchemaVersion ) ; keyspacesMap . put ( keySpace , thriftClient . describe_keyspace ( keySpace ) ) ; } catch ( InvalidRequestException e ) { System . err . println ( e . why ) ; } catch ( Exception e ) { throw new RuntimeException ( e . getMessage ( ) , e ) ; } } private void executeTruncate ( String columnFamily ) { } private void executeConsistencyLevelStatement ( Tree statement ) { } private void executeAssumeStatement ( Tree statement ) { } private void executeShowVersion ( ) throws TException { } private void executeShowKeySpaces ( ) throws InvalidRequestException , TException { } private void executeShowSchema ( Tree statement ) throws InvalidRequestException , TException { } private void showKeyspace ( StringBuilder sb , KsDef ksDef ) { } private void showColumnFamily ( StringBuilder sb , CfDef cfDef ) { } private void showColumnMeta ( StringBuilder sb , CfDef cfDef , ColumnDef colDef ) { }

Fix:
String rawColumName = CliUtils . unescapeSQLString ( statement . getChild ( 1 ) . getText ( ) ) ;